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A chimpanzee doesn’t hesitate to let it be known when he wants attention. Closest cousin to humans, this species of great ape has effective ways of communicating what it needs.
Researchers have often observed captive chimps pointing at an object they want their caregivers to give them or young chimps in the wild throwing tantrums to get their mother’s attention.
Until now, these behaviors were only observed when a chimpanzee wanted something. Recently, however, scientists documented footage of a wild adult chimpanzee showing a leaf to its mother, apparently just to share the experience with her, according to a study published Monday in the journal PNAS.
More examples of such interactions are needed to better understand the intention behind the gesture, the study researchers said, but the observation could demonstrate that chimpanzees possess social behavior once considered specific only to their human relatives. .
“Mostly, she didn’t seem to want her mother to do anything with the leaf. … She seems to show it just for the sake of showing it. It’s like, ‘look, look, that’s cool, isn’t it?’ And that’s very human and something that we thought was quite unique to our species,” said study co-author Katie Slocombe, a professor of psychology at the University of York in the UK.
The mother-daughter chimpanzees, called Sutherland and Fiona by the researchers, are part of the Ngogo chimpanzee community in Uganda’s Kibale National Park. Slocombe and her colleagues were studying Fiona and her baby as part of a separate project about their wider social group, when they captured the footage of Fiona holding the sheet to her mother before taking it back once she had Sutherland’s attention.
“It’s the first kind of promising suggestion that this (behaviour) might not be uniquely human, and that chimpanzees might be capable and motivated to do it,” Slocombe said.
Fiona had engaged in what the researchers call “leaf grooming,” a common behavior in which a chimpanzee strokes and manipulates a leaf. The reasoning behind the behavior is a mystery, but Slocombe and his colleagues suspect it could be inspecting an ectoparasite, like a tick, on top of the leaf. Often the surrounding chimps will also be engrossed in the action, staring intently at the leaf being groomed.
“When Fiona was doing that, (Sutherland) didn’t really seem interested; she didn’t look at her and paid her no attention. Fiona then shows him the sheet to say ‘look at it,'” Slocombe said. “She’s really persistent in trying to get her mum to look at her, and it wasn’t until her mum had obviously lowered her whole head to orient herself towards the sheet that (Fiona) then seemed satisfied.”
The researchers examined 84 video clips of chimpanzees grooming leaves near at least one other individual to look for possible explanations for the divergence from commonly observed behavior. The sample had a wide age range, with both male and female chimpanzees observed.
In more than 75% of cases, another person had either approached the leaf groomer or observed it very closely, the study team found. The vast majority of clips showed leaf grooming did not initiate social activity — such as grooming, playing together, or even eating the leaf — during or after the action, leading researchers to believe that Fiona was just looking to share an experience. with another monkey.
“Human infants, from around 10 months of age, will begin to bring things that they find interesting to their caregivers. … Just as Fiona did, they will extend their arm with the object in their hand towards their caregiver’s face. If the caregiver doesn’t respond, they will readjust and they will persist until the caregiver examines it,” Slocombe said.
Slocombe and his team always maintain a distance of 23 feet (7 meters) when observing chimpanzees in the wild, so as not to disturb them. This standard practice excludes the possibility that the behavior was learned from humans.
“Chimpanzees have been observed to place ectoparasites, found during grooming, on leaves and then try to crush them. In the clip, I can’t tell if that’s the case, but Fiona appears to be popping (something) out of her mouth, then placing it on the sheet and ‘showing’ it to her mother,” said Simone Pika, manager. from the Comparative BioCognition research group at the University of Osnabrück in Germany.
Pika was not involved in the work, but her team is also observing chimpanzees in Ngogo and plans to continue to seek additional evidence and clarification.
“We are still at the beginning of fully understanding the communicative complexity of chimpanzees and the implications for the evolution of human language and cognition,” Pika said. “We need a lot more data to clearly assess whether chimpanzees in the wild actually use declarative gestures and what their function is.”
This study is the first documented observation of this behavior in nature to suggest that monkeys have a motivation to share their experiences with each other, Slocombe said. She hopes this will encourage those who work with chimpanzees, in the wild or in captivity, to seek out other examples.
“What I really hope is that the publication of this result will kind of catalyze other people who have studied chimpanzees for a long time, maybe who have a lot of video footage of them, to think, “Oh wait. I’ve seen chimpanzees do something like this before, but I didn’t really think it was important,” Slocombe said.
“Maybe then we can start getting several examples to really better test if chimpanzee motivation is similar to humans.”